Surimi, the minced and refined flesh of fish, is prepared from a variety of fish, such as Alaska pollock, mackerel, Pacific whiting, hake from the South Pacific and South Atlantic, Pacific flatfish such as arrowtooth flounder and sardine. Such fish is filleted or eviscerated and split, then deboned and/or minced to obtain the flesh of the fish. Fish flesh is processed into surimi by a surimi process. Surimi can be processed from the flesh of fish on board processing ships or in land-based operations. The difference between at-sea processing and on land processing is that generally, fresh water is a scarce and expensive commodity for a factory vessel at sea.
Generally, surimi processing has involved obtaining appropriate fish material, removing fish muscle from frame by filleting, followed by mincing, washing, dewatering and refining. Under certain processing conditions, whole or split fish may be put through a meat separator/deboner without filleting. Minced meat is produced when flesh pieces are passed through a meat separator or mincer with drum openings of approximately 5 mm diameter. The mince is washed to remove water-soluble proteins and then dewatered. The cycle of washing and dewatering is usually repeated at least one more time. The washed, dewatered mince is refined or strained, then adjusted for moisture. Lastly, the meat is mixed with additives, packaged, frozen and stored ultimately to make a surimi product. More specifically, fresh water is used during the repeated washing procedure to remove water-soluble proteins and other materials from the minced meat.
Washing essentially concentrates the myofibrillar proteins of fish muscle (particularly actin and myosin) by washing away water-soluble proteins, pigments, and tissue debris that are also present in fish muscle. Where large quantities of fresh water are available, this can be accomplished by thoroughly washing and dewatering the minced meat in about three cycles.
In the standard surimi manufacturing process, the mince is often insufficiently washed onboard a factory trawler processing ship in an effort to conserve fresh water. The outside of the mince particles are efficiently washed but the inside does not contact water enough to effectively remove water soluble proteins and pigments remaining in the interior. To compensate for this problem, the washing and dewatering cycle is repeated, often several times to complete removal of water-soluble proteins, pigments and other tissue debris. As a result, fresh water is consumed in large quantities to complete the washing process. Depending on the condition of the fish, the resulting mince may become excessively hydrated during repeated washing, resulting in production of lower quality surimi, as determined by gel strength characteristics.
However, onboard a factory trawler processing ship, fresh water is often in short supply and can cost in the range of $15 to $25 per ton to produce fresh water from sea water by an energy-intensive reverse osmosis process. Therefore, there is a need in the art to develop an efficient surimi process that uses minimal amounts of fresh water for use onboard a factory trawler at sea. Moreover, even in a surimi processing operation on land, where fresh water is plentiful, repeated washing cycles, using large quantities of water, can reduce overall yield and quality due to excessive hydration. Accordingly, there is a need in the art to improve overall yield without increasing water consumption of surimi processing. There is a further need in the art to reduce water consumption without sacrificing quality of yield.